The operation failed the messaging interfaces have returned an unknown error (Solved)
Found this issue on a windows 7(32bit) pc running outlook 2010 pro plus (32bit)
I run a Google Apps environment so I’m running the Google Apps sync tool(GASMO).
This particular user needed both a google apps account and an exchange account running simultaneously.
Everything seemed fine but this error pops up when you try to add an email address to any existing contact or try to create a new contact with an email address.
I could create a new contact without an email address but not with.
After much googling with no decent results I just started trudging around in Outlook trying to find a solution. I saw that both the exchange and the Google Apps account had the same name for the contact list “contacts” so I renamed one and after a restart of outlook. Fixed!
Error Message:
The operation failed the messaging interfaces have returned an unknown error.
Solution:
In Contacts in Outlook:
Right click the google apps contact list: properties -> outlook address book (tab)
Rename the list from “contacts” to something else eg. “google contacts”
Restart Outlook
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